This invention relates to a solid fuel power plant of the type heretofore considered large for a mobile or portable plant. The present plant design utilizes features of the burner described in my U.S. Pat. No. 4,167,909, entitled Solid Fuel Burner, issued Sept. 18, 1979, and the boiler system described in my Patent Application, Ser. No. 050,621, entitled Free-Expansion Boiler with Replaceable Heat Exchanger Tubes, filed June 21, 1979.
As fuel costs escalate, it has become apparent that a substantial cost in the operation of a power plant has been the transportation costs in bringing the solid fuel to the plant for combustion and generation of steam and/or power. Often the class of fuel used to transport solid fuel is of a higher grade or in a more refined state than the fuel being transported. For example, contemporary trucks and trains utilize refined diesel fuel for moving burnable waste material or coal ores to the plant and removing ash from the plant, adding to the economic disadvantage of fixed site power plants. Furthermore, power plants are conventionally designed to operate on high Btu fuel, often necessitating careful selection of waste materials, ores and/or the preconditioning of wastes and partial refining of ores. Again, such preparation and refining conventionally utilizes a higher grade of fuel to accomplish the necessary processing than the substances being processed. The economic realities of such systems are self evident.
The advantages of the invented portable power plant are principally that it can be moved to the sites of the solid fuel and that it can consume solid fuel in a low Btu state.
For example, after a forestry operation there may be considerable slash and sawdust at the cutting site which is useable as fuel, but of such low value as to be insufficient to justify the expense of hauling to a fixed power plant. Also, the nearest power plant may be unable to utilize such a fuel. Because the waste material would be limited in quantity, and is generated only periodically, it is generally discarded or burned on site, contributing to environmental pollution. A portable power plant transported to the site would ideally consume the material, produce power with a minimum of pollution, and then be relocated elsewhere.
As a further example, in utilization of limited quantities or poor quality coal, it may be more efficient to move the plant to the ore body, exporting electrical power than to haul or refine the ore off site. Similarly, in large remote coal fields, local generation of steam and electrical power from low quality fuel material, otherwise discarded, would provide the energy needs for low cost, on site refining of select coal for export, thereby avoiding transportation of unrefined coal with included ash and moisture, to a distant refining plant or power plant.
Other advantages in a mobile or transportable power plant will become apparent on a detailed consideration of the preferred embodiment.